In the oil and gas industry, fluid samples are collected for analysis in many well applications. For example, in a subsea environment, tubing is used to convey well fluid to a desired location. Measurements and samples of the fluid moving through the tubing can provide useful information for improved operation of the well.
Fluid samples, for example, may be collected for reservoir characterization or to deduce reservoir fluid properties. The analysis generally is done at a land-based or field-deployed pressure/volume/temperature (PVT) laboratory. The information derived is used for periodic reservoir characterization over the life of a well to facilitate the evaluation of reserves, and for production planning and optimization.
Fluid samples are also collected to enable deposition studies, for example, samples may be collected to carry out asphaltene deposition studies. In subsea applications, problematic deposition of such materials can occur as a result of the temperature and pressure gradients between a subsea wellhead and the surface.
In many of these same well applications, PVT data and hydrogen sulphide (H2S) level data are used to facilitate optimization of a well fluid production.
The PVT data, for example, can be used to correct volumetric correlations applied to flow meters, pipelines and other downstream assets. However, the detection of the various well parameters and the taking of samples for further analysis can be difficult and/or inefficient, particularly in certain environments, such as subsea environments.
Subsea sampling can be applied to single-phase or multiphase fluids. When the fluid is multiphase, the phases can be collected separately and analyzed independently. This information can be used to reduce the uncertainty of the results obtained by using multiphase flow meters.
Various apparatus, methods and systems for sampling and analyzing well fluids have been identified previously, including those used subsea. U.S. Pat. No. 6,435,279 discloses a method and apparatus for sampling fluids from an undersea wellbore utilizing a self-propelled underwater vehicle, and a collection and storage device.
International patent application PCT/EP2008/050445, published as WO 2008/087156, discloses a system and method for analysis of fluid samples. An article entitled “Improved Production Sampling Using the Framo Multiphase Flow Meter” by Framo Engineering AS (October 1999) discusses a multiphase flow meter used in fluid sampling including subsea with the aid of remotely operated vehicles (ROV).
Other technologies, such as Schlumberger's MDT sampling and analysis technologies also have been used for subsea sampling and analysis of fluids in the oil and gas industry. A further well known system used by Schlumberger for sampling fluids in the oil and gas industry is discussed in international patent application PCT/EP2005/010580, published as WO 2006/037565, the disclosure of which is hereby incorporated by reference.